3D printing basic knowledge

Part1:Defination

3D printing refers to processes in which material is joined or solidified under computer control to create a three-dimensional object, with material being added together (such as liquid molecules or powder grains being fused together). 3D printing is used in both rapid prototyping and additive manufacturing (AM). Objects can be of almost any shape or geometry and typically are produced using digital model data from a 3D model or another electronic data source such as an Additive Manufacturing File (AMF) file (usually in sequential layers).

1. Hull define the STL (Stereolithography) file format and the digital slicing and infill strategies common to many processes today.We can find in right picture:STL file format is to encode the surface geometry of a 3D object using a simple concept called “tessellation”. And I will introduce the detail in "format part"

2. AMF(Additive Manufacturing File Format), It was introduced as the ASTM standard file format for 3D printing in 2011 as an alternative to the de-facto industry standard STL file format. AMF is an XML-based format designed to contain native support for file specifications such as geometry, scale, color, material, lattices, duplicates, and orientation

The basic workflow of 3D printing is the following:

• We design it in CAD software and output 3D printing format(stl,obj,amf);
• Slice software will translate to 3D printing language according to our configuration
• Update data to 3D printing and then run it

Part2. Machine and material

The following is several common types of 3D printing and I will introduce most of them

SLA

Stereolithography (SLA or SL; also known as stereolithography apparatus, optical fabrication, photo-solidification, or resin printing) is a form of 3-D printing technology used for creating models, prototypes, patterns, and production parts. It is very popular in industry because the quality is cool and the performance is similar with engineer plastic

SLA runs in a layer by layer fashion using photopolymerization, a process by which light causes chains of molecules to link, forming polymers.Those polymers then make up the body of a three-dimensional solid.

DLP

DLP 3D printer uses a digital light projector (DLP) as the light source for curing photo-reactive polymers. DLP offers a brilliant, colorful, clear image with good contrast. The real disadvantage of DLP projectors is what devotees call the "rainbow effect." Consumer DLP projectors use a transparent colored disk (chromatic wheel) which turns in front of the lamp. This disk, divided into several primary colors, reconstitutes all the final colors.

DLP and SLA is simialr ,the following figure is the compare of DLP and SLA

SLS/SLM

1. Selective Laser Sintering (SLS) is an additive manufacturing process that belongs to the Powder Bed Fusion family. In SLS, a laser selectively sinters the particles of a polymer powder, fusing them together and building a part layer-by-layer. The materials used in SLS are thermoplastic polymers that come in a granular form.

2. Selective laser melting (SLM) is a particular rapid prototyping use a high power-density laser to melt and fuse metallic powders together. In many SLM is considered to be a subcategory of Selective Laser Sintering (SLS). The SLM process has the ability to fully melt the metal material into a solid 3D-dimensional part unlike SLS.

   

   Figure13:The basic structure of SLS

   

   Figure14:The SLS printing process

3. Here is how the SLS fabrication process works:

   • The powder bin and the build area are first heated just below the melting temperature of the polymer and a recoating blade spreads a thin layer of powder over the build platform.
   • A CO2 laser then scans the contour of the next layer and selectively sinters (fuses together) the particles of the polymer powder. The entire cross section of the component is scanned, so the part is built solid.
   • When the layer is complete, the build platform moves downwards and the blade re-coats the surface. The process then repeats until the whole part is complete.

4. Advantage/Disadvantage

   • SLS/SLM allows for the construction of complex parts that are both durable and provide better functionality when compared to other Additive Manufacturing (AM) methods.
   • The biggest problem of the technology is that the fabricated parts can be porous and/or have a rough surface depending on the used materials. Another problem, mainly for polymer parts, is thermal distortion. This can cause shrinking and warping of fabricated parts. These are two things to keep in mind when designing products to be fabricated using SLS printers. Figure15: Comparing gander below and see how SLS, FDM and SLA

1. The application of SLS/SLM

FDM

Fused Deposition Modeling (FDM), or Fused Filament Fabrication (FFF), is an additive manufacturing process that belongs to the material extrusion family. In FDM, an object is built by selectively depositing melted material in a pre-determined path layer-by-layer. The materials used are thermoplastic polymers and come in a filament form.FDM is the most widely used 3D printing technology: it represents the largest installed base of 3D printers globally and is often the first technology people are exposed to. In this article, the basic principles and the key aspects of the technology are presented.

One of the key strengths of FDM is the wide range of available materials. These can range from commodity thermoplastics (such as PLA and ABS) to engineering materials (such as PA, TPU, and PETG) and high-performance thermoplastics (such as PEEK and PEI).

other machine

Laminated Object Manufacturing (LOM)

LOM is a rapid prototyping system developed by Helisys Inc. (Cubic Technologies is now the successor organization of Helisys) In it, layers of adhesive-coated paper, plastic, or metal laminates are successively glued together and cut to shape with a knife or laser cutter. Objects printed with this technique may be additionally modified by machining or drilling after printing.

PolyJet

PolyJet is a powerful 3D printing technology that produces smooth, accurate parts, prototypes and tooling. With microscopic layer resolution and accuracy down to 0.1 mm, it can produce thin walls and complex geometries using the widest range of materials available with any technology.

Benefits of PolyJet:

• Create smooth, detailed prototypes that convey final-product aesthetics;
• Produce accurate molds, jigs, fixtures and other manufacturing tools;
• Achieve complex shapes, intricate details and delicate features.
• Incorporate the widest variety of colors and materials into a single model for unbeatable efficiency.

Part3.advantage and disadvantage

Advantage

1. Speed:Complex designs can be uploaded from a CAD model and printed in a few hours. The advantage of this is the rapid verification and development of design ideas. The ability to produce functional end parts at low to mid volumes offers a huge time-saving advantage when compared to traditional manufacturing techniques (often the lead time on an injection molding die alone can be weeks).
2. Wide resolution range(micro objects to building)
3. Complex structure otherwise impossible to make
4. Lightweight(no joint overhead)
5. Stronger(all in one part=no joint failure)
6. Single step manufacture Figure31: The 3D printing process (red) compared to the traditional manufacturing process (black) One of the biggest concerns for a designer is how to manufacture a part as efficiently as possible. Most parts require a large number of manufacturing steps to be produce by traditional technologies. The order these steps occur affects the quality and manufacturability of the design.

7. Cost The cost of manufacture can be broken down into 3 categories; machine operation costs, material cost and labor costs.

8. Machine operation costs( the ability to produce complex geometries in a single step results in higher efficiency and turnaround. Machine operation costs are typically the lowest contributor to the overall cost of manufacture)

9. Material costs: Material costs are the biggest contributor to the cost of a part made via additive manufacturing.There are less waste
10. Labor costs: One of the main advantages of 3D printing is the the low cost of labor. Post-processing aside, the majority of 3D printers only require an operator to press a button. Compared to traditional manufacturing, where highly skilled machinists and operators are typically required, the labor costs for a 3D printer are almost zero.

reference from 3D hub

Disadvantage

1. Limited Materialsthe materials that can be used are still limited.The kinds of plastic vary among the likes of high-strength and high temperature materials, so part strength can't accurately be tested in many cases.
2. Questionable Accuracy:Many materials print to either +/- 0.1 mm in accuracy, meaning there is room for error.
3. Manufacturing Limitations3D printing is perfect for creating prototype parts because it's an economical, inexpensive way of creating one-run parts for which you don't have to create tooling. In terms of a manufacturing process, 3D printing is not a realistic option as of the date of publication. In manufacturing processes such as thermoforming and stamping, several parts are typically made in one minute, not hours.
4. Size:Parts created additively through 3D printing are also limited in size.

Attacment:

1. platform_level
2. testsupport model
3. ctrlv-3d-test model
4. test printing